An MRI apparatus uses a uniform static magnetic field, and the static magnetic field thereof changes locally depending on the magnetic susceptibility of an object. The effect of the local magnetic field change appears in image data as change of a phase. The imaging method that emphasizes the phase change by arithmetic processing is known as susceptibility-emphasized imaging (Patent Document 1). Susceptibility-emphasized imaging has received attention as a method effective for MR angiography of a venous blood vessel, since it is capable of emphasizing magnetic susceptibility due to deox hemoglobin in the blood.
However, since susceptibility-emphasized imaging uses the phase change generated by magnetic susceptibility, the imaging needs the echo signal at a point where it passed about 70 ms from irradiation of an RF pulse. As a result, repetition time (TR) of a pulse sequence (hereinafter simply abbreviated as sequence) can not be set short, whereby taking a long period of time for imaging.
On the other hand, the echo planar method or the fast spin echo method are known as methods for reducing the imaging time in MRI apparatuses by measuring a plurality of echo signals in one time of RF pulse irradiation. Patent Document 2 discloses an example of susceptibility-emphasized imaging using the echo planar method to reduce the imaging time.    Patent Document 1: U.S. Pat. No. 6,501,272    Patent Document 2: U.S. Pat. No. 7,154,269
As mentioned above, magnetic susceptibility can be increased by prolonging the echo time as previously mentioned. In the case that the echo planar method is applied to susceptibility-emphasized imaging, since the echo signal having a long echo time tends to be greatly attenuated, the unsolved problem remains that the signal-to-noise ratio deteriorates when an image is reconstructed from such echo signals.